1. Field of the Invention
The present invention relates to oil well downhole tools and more particularly to an improved firing mechanism for firing a perforating gun wherein an improved oil dampened firing mechanism allows the tool to be lowered on a slick line having no through bore, with a jar mechanism carried by the slick line used to fire the mechanism.
2. General Background
When drilling oil wells, typically a vertical hole is drilled in the ground and relatively large diameter pipe (called casing) is inserted in the hole to prevent the walls of the hole from collapsing into the hole. When it is desired to produce the well, it is necessary to make holes in the casing to allow the oil to enter the bore of the casing and travel upward to the surface. A common way of perforating the casing is to lower a perforating gun into the hole until it reaches a point where the perforations are desired. The perforating gun has a timer, and is set at the surface to go off a certain amount of time after pins are sheared which activates the timer. Unfortunately, if the perforating gun gets stuck on the way down to the production center, there is no way to turn off the timer. The perforating gun may sometimes fire at the wrong location, producing unwanted and unnecessary perforations in the casing which could allow gas under pressure to enter the casing and cause a blow out of the well.